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N.A.C.A.. Technical Memorandum No. 701 3The results of closing the gap were distinctly notice-able on the general behavior of the airplane by a lowerstick force and enhanced elevator effect. Although no -.tail landings could be made with gap open, the elevatoreffect, with gap closed, was such as to make the tail skidtouch the ground ahead of the wheels.The size and the method of closing the gap is indi-cated in Figure 2. A strip of varnished linen is glued tostabilizer and elevator.In Figure 3 the lift coefficients are plotted againstthe elevator displacement with open and closed gap for thesame c.g. position. The change in elevator displacementwith the lift factor aS/ca is shown in Figure 4 versusthe c.g. position, along with the magnitude of the staticstability by fixed control acm/aca.* According to figure4 the limit of the static stability with fixed controllies, for open gap and full throttle, at 26.7 c.g. posi-tion, at 28.6 per cent of the mean wing chord with closedgap and at 34.9 and 36.9 per cent of the mean wing chordin throttled flight.dcmThe static elevator effect is d = 0.024 for opengap in flight with full throttle and = 0.012 withthrottle closed. With gap closed the static elevator ef-dcm dofect is ---= 0.034, with throttle open and dcm = 0.015dp apwith throttle closed.Figure 5 exhibits the results of stick force measure-ments with open and closed gap. The reduction in stickforce by closing the gap amounts to about 1.5 kg (3.3 lb.)in flight with open throttle, or about 60 per cent by lowdynamic pressures, and 30 per cent by high dynamic pres-sures. The improvement in throttled flight lies withinmeasuring accuracy.The moments impressed by the weight of the elevatorcontrol affect the forces which the pilot exerts on the*According to experience and in agreement with thbo6reticalconsiderations the relationship of Ecm/aca to c.g. posi-tion r is approximately